# Third law of thermodynamic as function of equilibrium constant

1. Mar 1, 2010

### kthouz

Hello!
Here is an equation that i sometimes use in calculating enthalpy of reaction aA+bB=cC+dD.
a,b,c and d are stoechiometric coefficients, A,B,C and D are chemical compounds in reaction. They say that is an other form of the third law of thermodynamic, can one guide me please to derive it?
$$\Delta$$H=T[$$\Delta$$$$\Phi$$-Rln(K)].
where T is temperature, $$\Delta$$$$\Phi$$ is the Gibbs Free energy, R is the ideal gas constant and K is the partial pressure equilibrium constant.